The present invention relates to improvements in corner pieces for duct connectors.
In particular, it relates to an improvement in the duct connector disclosed in U.S. Pat. No. 4,461,499 to Hunter et al. entitled "Transverse Joint System for Sheet Metal Ducts", the entire disclosure of which is incorporated herein by reference. That patent is assigned to the assignee of the present application and it depicts a system for connecting sheet metal duct sections. That system has proven to be very useful over the years. It includes abutting sections of sheet metal ducts, joining them at an interface by flanging the ends of each section adjacent the interface and forming a plurality of spaced tabs in the wall surface of the flanges, which tabs protrude outwardly in a direction away from the interface. A generally V-shaped coupling member having a portion of free edges thereof folded back under the corresponding side wall is then assembled over a pair of opposed flanges with the edges of the folded-under portions snapping in behind the tabs to lock the flanges together. Such V-shaped coupling members are arrayed around the periphery of the duct and, at their intersection are interleaved. The coupling members are secured by drilling the interleaved portions and joining them with a nut and bolt arrangement. In an alternative embodiment, the interleaved corners are surrounded by an outer corner piece which is crimped to secure them together.
The coupling members according to the prior patent omit the folded back free edges at their ends so that there is no interference with the interleaving of the intersecting coupling members. Forming the coupling members without the folded free edge at this end and providing the holes through which the bolt is passed is not a problem for those who have the appropriate tools for doing so. In practice the coupling members have had their ends stamped to have the folded edges placed closer to the sides of the V, permitting the interleaving of the sides to form the corners. However, the stamped product still needs to be drilled, and the stamping and drilling apparatus are not widely available. Without having the appropriate tools available, obtaining proper sized coupling members according to the prior invention is difficult, at best.
The present invention is directed toward improving on the prior transverse joint system by providing corner pieces which may be used in connection with V-shaped coupling members according to our prior patent, but not necessitating the use of special tools.
It does so in part by providing a corner member which can be used with a V-shaped coupling member simply cut from a running length of stock material, without other special metal-working tools being needed. Thus, the V-shaped coupling members can be distributed in standard lengths and be cut to suit the needs of particular job without necessitating the use of special tools.